Primary efflorescence Primary efflorescence is named such, as it typically occurs during the initial cure of a
cementitious product. It often occurs on
masonry construction, particularly
brick, as well as some
firestop mortars, when water moving through a wall or other structure, or water being driven out as a result of the heat of hydration as cement stone is being formed, brings salts to the surface that are not commonly bound as part of the cement stone. As the water evaporates, it leaves the salt behind, which forms a white, fluffy deposit, that can normally be brushed off. The resulting white deposits are referred to as "efflorescence" in this instance. In this context efflorescence is sometimes referred to as "saltpetering." Since primary efflorescence brings out salts that are not ordinarily part of the cement stone, it is not a structural, but, rather, an aesthetic concern. For controlling primary efflorescence, formulations containing liquid fatty acid mixtures (e.g., oleic acid and linoleic acid) have commonly been used. The oily liquid admixture is introduced into the batch mix at an early stage by coating onto the sand particles prior to the introduction of any mix water, so that the oily admixture is distributed uniformly throughout the concrete batch mix.
Protecting against efflorescence It is possible to protect porous building materials such as brick, tiles, and concrete against efflorescence by treating the material with an impregnating, hydro-phobic sealer. This is a sealer that repels water and will penetrate deeply enough into the material to keep water and dissolved salts well away from the surface. However, in climates where freezing is a concern, such a sealer may lead to damage from freeze/thaw cycles. And while it will help to protect against efflorescence, it cannot permanently prevent the problem. Common rebar protective measures include the use of epoxy coating. Certain cement types are less resistant to chlorides than others. The choice of cement, therefore, can have a large effect upon the concrete's reaction to chlorides. Today's water repellents help create a vapor permeable barrier; liquid water, especially from wind driven rains, will stay out of the brick and masonry. Water vapor from the interior of the building, or from the underside of pavers can escape. This will reduce efflorescence, spalling and scaling that can occur from water being trapped inside the brick substrate and freezing during cold weather. Years ago, the water repellents trapped moisture in the masonry wall creating more problems than they solved. Condensation in areas that experienced the four seasons were much more problematic than their counterparts.
Image gallery Image:Ausblühungen.JPG|Primary efflorescence on a brick wall in
Germany. Image:K10 primary efflorescence.jpg|Primary efflorescence on a
firestop mortar at
Mississauga Civic Centre in
Mississauga, Ontario City Hall. Image:Efflorescence.JPG|Substantial primary efflorescence on a building in
Denver, Colorado. Image:Secondary efflorescence 1 of 2.jpg|Secondary efflorescence - dissolving the cement stone and attacking rebar Image:Secondary efflorescence 2 of 2.jpg|Secondary efflorescence Image:Concrete stalactite.jpg|Concrete derived secondary deposit of calcium carbonate creating
calthemite stalactites, which can be mistakenly confused with efflorescence. ==See also==